1. Field of the Invention
The present invention pertains to processing products in filled containers, and more particularly relates to a method and apparatus for purging air from containers such as pouches prior to closing and sealing the same.
2. Description of the Prior Art
It is well known that it is essential for air to be purged from containers filled with a food or other easily oxidized products prior to sealing the containers in order to minimize oxidation of the product and thus provide a high quality pack. Prior art methods and apparatus for purging air from containers by flushing with neutral gases, vacuum, high pressure steam, or low pressure steam within steam tunnels are well known in the art. Many known prior art purging systems require costly apparatus such as steam tunnels, or require equipment to move snorkel tubes into and out of the containers. The operating costs of these and other purging systems are high because they require excessive amounts of neutral gases such as carbon dioxide, or steam at high pressure and/or at superheated temperatures for purging the air from the containers. Many of these prior art systems are also too complicated and/or do not efficiently remove air from the pouch.
Assignee's prior art United States patent to Wilson et al which issued as U.S. Pat. No. 4,016,705 on Apr. 12, 1977 discloses two prior art systems for purging air from filled pouches. Both of these purging systems require the open upper end of the pouch to pass through a steam atmosphere in a steam tunnel. One of the systems requires that a steam nozzle be reciprocated into and out of the pouch during purging and that a high pressure jet of steam be directed into the pouch through the nozzle while steam at a lower pressure flows downwardly past the outer walls of the pouch to remove air from the pouch. The other Wilson et al system directs steam into the headspace of the pouch between spaced baffle plates that are secured to the walls of the tunnel for directing the downward flow of steam into the headspace and to prevent a direct flow of steam downwardly between the tunnel walls and the external surfaces of the pouch for providing an avenue for the purged air to escape.
United States Johnson U.S. Pat. No. 4,081,942 which issued on Apr. 4, 1978 discloses an intermittently driven machine for filling two types of products into a pouch, and purging air from the filled pouch while the pouch is in the ambient atmosphere at a steaming station by means of a continuous flow of steam at approximately 450.degree. F. into the open end of the pouch from a nozzle located just above the open end of the pouch.
Other United States patents such as Davis U.S. Pat. No. 2,107,237; Kronquest U.S. Pat. No. 2,240,655; Minaker U.S. Pat. No. 2,285,867 and Marx U.S. Pat. No. 2,317,470 move containers through steam tunnels for purging air from the containers.